Ignition switch itself, or the connector on the switch

Firewall connector

Firewall mounted relay

If it's an automatic, could be the neutral safety switch either bad, out of adjustment, or something changed in the shifter adjustment.

Any connectors or wireing in between

I'll go get the crowbar so I can pry out of you what you've tried to do, what kind of test gear you have, and whether this thing is an automatic or a stick